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Questions and Answers
What is the main reason for physiologic V/Q inequality?
What is the main reason for physiologic V/Q inequality?
What happens to much of the oxygen in the upper portions of the lungs due to physiologic V/Q inequality?
What happens to much of the oxygen in the upper portions of the lungs due to physiologic V/Q inequality?
How do pathological mismatches affect arterial PO2?
How do pathological mismatches affect arterial PO2?
What effect does physiologic V/Q inequality have on O2 diffusion?
What effect does physiologic V/Q inequality have on O2 diffusion?
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How does the process of diverting blood away from a diseased area to a healthy area help in cases of decreased air flow to a region of the lung?
How does the process of diverting blood away from a diseased area to a healthy area help in cases of decreased air flow to a region of the lung?
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What is the initial step for oxygen to diffuse in the alveolus?
What is the initial step for oxygen to diffuse in the alveolus?
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Where does the oxygen primarily hydrogen bond once it enters the plasma?
Where does the oxygen primarily hydrogen bond once it enters the plasma?
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Which process allows oxygen to enter the RBC cytoplasm after crossing two cell's membranes?
Which process allows oxygen to enter the RBC cytoplasm after crossing two cell's membranes?
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What happens to the oxygen bound to hemoglobin as the plasma empties of O2?
What happens to the oxygen bound to hemoglobin as the plasma empties of O2?
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What drives the movement of dissolved oxygen from the plasma to the peripheral tissues?
What drives the movement of dissolved oxygen from the plasma to the peripheral tissues?
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What condition needs to be met for the pO2 of the plasma to equal that of the periphery during the process of oxygen diffusion?
What condition needs to be met for the pO2 of the plasma to equal that of the periphery during the process of oxygen diffusion?
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What does a left shift in the oxygen dissociation curve indicate about the binding of hemoglobin to oxygen?
What does a left shift in the oxygen dissociation curve indicate about the binding of hemoglobin to oxygen?
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How does a decrease in pH affect the binding of hemoglobin to oxygen?
How does a decrease in pH affect the binding of hemoglobin to oxygen?
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What effect does an increase in temperature have on the binding of hemoglobin to oxygen?
What effect does an increase in temperature have on the binding of hemoglobin to oxygen?
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How do pulmonary blood vessels respond to decreased Po2?
How do pulmonary blood vessels respond to decreased Po2?
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Study Notes
Physiologic V/Q Inequality
- Main reason for physiologic V/Q inequality is the uneven distribution of ventilation and perfusion in the lungs.
- In the upper lung areas, much of the oxygen is not fully utilized due to inadequate blood flow relative to ventilation, leading to wasted ventilation.
Pathological Mismatches and Arterial PO2
- Pathological V/Q mismatches result in reduced arterial PO2 levels, leading to hypoxemia and potential systemic effects.
- These mismatches increase the risk of diffusion impairment, further affecting oxygen transfer to the bloodstream.
Oxygen Diffusion and Physiologic V/Q Inequality
- Physiologic V/Q inequality negatively impacts oxygen diffusion efficiency due to uneven blood flow, causing some parts of the lung to be over-ventilated relative to perfusion.
- Improved airflow to a healthy area compensates by diverting blood from less ventilated regions, optimizing gas exchange.
Oxygen Diffusion Initial Steps
- The diffusion process begins with oxygen entering the alveolus from the air, then traveling across the alveolar-capillary membrane into the blood plasma.
- Oxygen primarily forms hydrogen bonds with plasma proteins once dissolved in the blood.
Oxygen Transport in RBCs
- The process known as diffusion permits oxygen to enter red blood cells (RBCs) after crossing the alveolar membrane and capillary endothelial cells.
- Bound oxygen to hemoglobin is released as the plasma's O2 concentration decreases, ensuring a balance in oxygen delivery.
Driving Forces and Plasma pO2
- Movement of dissolved oxygen from plasma to peripheral tissues is driven by concentration gradients, favoring diffusion into areas of lower O2 concentration.
- For plasma pO2 to equal that of the peripheral tissues, a condition of equilibrium must be achieved, reflecting efficient diffusion processes.
Oxygen Dissociation Curve Dynamics
- A left shift in the oxygen dissociation curve indicates increased affinity of hemoglobin for oxygen, meaning hemoglobin binds oxygen more readily.
- Decreased pH (acidosis) leads to decreased hemoglobin affinity for oxygen, enhancing oxygen unloading to tissues (Bohr effect).
- Increased temperature reduces hemoglobin's affinity for oxygen, facilitating oxygen delivery to active tissues.
Pulmonary Blood Vessels Response
- Pulmonary blood vessels respond to decreased PO2 by vasoconstricting, directing blood flow towards better-ventilated areas of the lung to optimize gas exchange.
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